I had a similiar experience with my 95 at 50k miles. It ended up being the O2 sensor.
Found out the ECM runs in a closed loop mode until exhausts temp reaches 200+ , subbsequentlythe defective O2 sensor sends incorrect data to the ECM and screws up the mix and timing.
Good luck.
O.K have now replaced Opti spark, Water pump, wires. hoses and done a little much needed detailing.
Took her for a spin and had the same scenario. After doing more reading it appears that the ECS runs in a open loop until the O2 sensor reaches about 600F, then goes into a closed loop mode were...
black.
I have pulled the plugs and found that the pssenger side all look great, the drivers side all look powdery black (not oil).
Again I think this points to opti spark.
Engine code was 0016.
Mostly highway. I have removed the opti spark and observed a yellow ish residue.
by the looks of the rotar and cap there has definately been some spark issues here.
Thanks for the info. I have put it up on blocks and currently making my way to the opti spark. I'll have the ICM tested this weekend.
I did find moisture at the weep hole of the water pump, also looks like a small leak at the front oil seal, some vacuum lines look weak as well.
NOTE: I should...
yah I eventually get check engine soon light and then goes off.
Funny thing is it appears to clear up once the light comes on then rough again after going out.
Onefast95vette; I too have similiar problem, however my sputtering does not always begin when temp hits 190, it appears more random. but does start clean and goes downhill from there.
Wierd, but when the check engine light comes on it appears to clear up, until it subsequently goes off again...
Just bought a C4 with 46K on it.
of course I did'nt catch all the gotchas.
Today (my first lengthy ride) Drove great for 20-30 miles until I came to the first stop light after 20 miles, began running rough and smokes with a little acceleration. (Possibly oxygen semsors).
Mike
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